Heat pump water heater appliance

ABSTRACT

A water heater appliance includes a sealed system and an electric heating element. The sealed system and electric heating element are configured for heating water within an interior volume of a tank. A temperature sensor is mounted to the tank. The electric heating element is positioned below the temperature sensor within the interior volume of the tank.

FIELD OF THE INVENTION

The present subject matter relates generally to water heater appliances, such as heat pump water heater appliances.

BACKGROUND OF THE INVENTION

Certain water heater appliances include a tank therein. Heating elements, such as sealed systems, gas burners, electric resistance elements, or induction elements, heat water within the tank during operation of such water heater appliances. In particular, the heating elements generally heat water within the tank to a predetermined temperature. The predetermined temperature is generally selected such that heated water within the tank is suitable for showering, washing hands, etc.

During operation, relatively cool water flows into the tank, and the heating elements operate to heat such water to the predetermined temperature. Temperature sensors are typically included in water heater appliances to, among other things, determine the temperature of the water in the tank. Many water heater appliances utilize multiple temperature sensors. However, a recent trend has been to utilize a single temperature sensor, to reduce the cost of the water heater appliance.

Recently, methods have been developed for utilizing temperature sensors to determine a volume of water added to the tank during flow events. Algorithms have also been developed which correspond temperature decay for water within the tank to the added water volume. Such methods are disclosed, for example, in U.S. Patent Application Publication No. 2010/0206869 entitled “Heat Pump Water Heater Control,” U.S. Pat. No. 8,422,870 entitled “Residential Heat Pump Water Heater,” and U.S. Patent Application Publication No. 2012/0145095 entitled “Residential Heat Pump Water Heater,” all of which are incorporated by reference herein in their entireties.

Operating heat pump water heater appliances with a single temperature sensor during the Department of Energy's first hour delivery rating (FHR) test poses certain challenges. During the FHR test, heated water is drawn from a top of the tank, and relatively cool water enters the tank through a dip tube. A supplementary electrical heating element operates in response to the single temperature sensor in order to heat the added water. Generally, the single temperature sensor and the supplementary electrical heating element are positioned directly adjacent each other at a top of the tank in order to intensify heat transfer to water at the top of the tank and maximize the volume of heated water generated during the FHR test. However, accurately determining the volume of water added to the tank with the single temperature in such a configuration can be difficult. For example, the single temperature sensor is preferably positioned adjacent an anti-siphon hole at a top portion of tank in order to permit the single temperature sensor to measure the temperature of water within the tank at the top portion of the tank.

Accordingly, a water heater appliance with features for providing large volumes of heated water during a one hour period would be useful. In particular, a water heater appliance having a single temperature sensor for measuring the temperature of water within a tank of the water heater appliance that also includes features for providing large volumes of heated water during a one hour period would be useful.

BRIEF DESCRIPTION OF THE INVENTION

The present subject matter provides a water heater appliance. The water heater appliance includes a sealed system and an electric heating element for heating water within an interior volume of a tank. A temperature sensor is mounted to the tank. The electric heating element is positioned below the temperature sensor within the interior volume of the tank. Additional aspects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention.

In a first exemplary embodiment, a water heater appliance defines a vertical direction. The water heater appliance includes a tank that defines an interior volume. A sealed system is configured for heating water within the interior volume of the tank. A dip tube is mounted to the tank. The dip tube extends into the interior volume of the tank. A temperature sensor is mounted an outer surface of the tank. The temperature sensor is configured for measuring a temperature of water within the interior volume of the tank. An electric heating element is mounted to the tank. At least a portion of the electric heating element is positioned within the interior volume of the tank. The electric heating element is positioned below the temperature sensor along the vertical direction. The electric heating element is spaced apart from the temperature sensor along the vertical direction by a distance. The distance is greater than one inch and less than twenty-four inches.

In a second exemplary embodiment, a heat pump water heater appliance defines a vertical direction. The heat pump water heater appliance includes a tank that defines an interior volume. The tank extending between a top portion and a bottom portion along the vertical direction. A shroud is positioned at the top portion of the tank. A sealed system is configured for heating water within the interior volume of the tank. The sealed system includes a compressor, an evaporator and a condenser. The compressor and evaporator are positioned within the shroud. The condenser is positioned on the tank. A dip tube is mounted to the tank at the top portion of the tank. The dip tube extends downwardly along the vertical direction into the interior volume of the tank. A temperature sensor is positioned at an outer surface of the tank. The temperature sensor is configured for measuring a temperature of water within the interior volume of the tank. An electric heating element is mounted to the tank and extends into the interior volume of the tank. The electric heating element is configured for heating water within the interior volume of the tank. The electric heating element is positioned below the temperature sensor along the vertical direction by a distance. The distance is greater than one inch.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.

FIG. 1 provides a perspective view of a water heater appliance according to an exemplary embodiment of the present subject matter.

FIG. 2 provides a schematic view of certain components of the exemplary water heater appliance of FIG. 1.

FIG. 3 provides a side partial, sectional view of a tank of the exemplary water heater appliance of FIG. 1.

FIG. 4 provides a perspective view of the tank of the exemplary water heater appliance of FIG. 1.

FIG. 5 provides an elevation view of a distal end of a dip tube of the exemplary water heater appliance of FIG. 1.

FIG. 6 provides a perspective view of the distal end of the dip tube of FIG. 5.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

FIG. 1 provides a perspective view of a water heater appliance 100 according to an exemplary embodiment of the present subject matter. Water heater appliance 100 includes an outer shell or casing 102. Casing 102 generally surrounds a tank 112 (FIG. 2) such that tank 112 is disposed within casing 102. Casing 102 may be formed from a variety of components. As illustrated, casing 102 may include a wrapper 154, one or more covers, such as a top cover 156 and a bottom cover 158 as illustrated, and a shroud 159 positioned at or adjacent a top portion 108 of water heater appliance 100. Covers 156, 158 may be fastened or coupled to wrapper 154 and shroud 159 to form casing 102.

Upper and lower heating elements 118, 119 (FIG. 2) and a sealed system 120 (FIG. 2) may also be positioned within casing 102 for heating water within tank 112. Upper and lower heating elements 118, 119 can be any suitable heating elements. For example, upper heating element 118 and/or lower heating element 119 may be an electric resistance element, a microwave element, an induction element, or any other suitable heating element or combination thereof. Lower heating element 119 may also be a gas burner. As will be understood by those skilled in the art and as used herein, the term “water” includes purified water and solutions or mixtures containing water and, e.g., elements (such as calcium, chlorine, and fluorine), salts, bacteria, nitrates, organics, and other chemical compounds or substances.

Water heater appliance 100 also includes an inlet or cold water conduit 104 and an outlet or hot water conduit 106 that are both in fluid communication with a chamber or interior volume 114 (FIG. 2) defined by tank 112. As an example, cold water from a water source, e.g., a municipal water supply or a well, can enter water heater appliance 100 through cold water conduit 104. From cold water conduit 104, such cold water can enter interior volume 114 of tank 112 wherein it is heated with heating elements 118, 119 and/or sealed system 120 to generate heated water. Such heated water can exit water heater appliance 100 at hot water conduit 106 and, e.g., be supplied to a bath, shower, sink, or any other suitable feature.

Water heater appliance 100 extends longitudinally between a top portion 108 and a bottom portion 109 along a vertical direction V. Thus, water heater appliance 100 is generally vertically oriented. Water heater appliance 100 can be leveled, e.g., such that casing 102 is plumb in the vertical direction V, in order to facilitate proper operation of water heater appliance 100. A drain pan 110 is positioned at bottom portion 109 of water heater appliance 100 such that water heater appliance 100 sits on drain pan 110. Drain pan 110 sits beneath water heater appliance 100 along the vertical direction V, e.g., to collect water that leaks from water heater appliance 100 or water that condenses on an evaporator 128 (FIG. 2) of water heater appliance 100. It should be understood that water heater appliance 100 is provided by way of example only and that the present subject matter may be used with any suitable water heater appliance, including for example a heat pump water heater appliance.

FIG. 2 provides a schematic view of certain components of water heater appliance 100. As may be seen in FIG. 2, water heater appliance 100 may include sealed system 120 for heating water within interior volume 114 of tank 112. Sealed system 120 generally operates in a heat pump cycle. Thus, water heater appliance 100 is commonly referred to as a “heat pump water heater appliance.” Water heater appliance 100 may additionally include one or more auxiliary heating elements, such as upper heating element 118 and/or lower heating element 119.

Sealed system 120 may include a compressor 122, a first condenser 124, a second condenser 126 and an evaporator 128. Compressor 122 and/or evaporator 128 of sealed system 120 may be disposed within casing 102 at top portion 108 of water heater appliance 100. As is generally understood, various conduits may be utilized to flow refrigerant between the various components of sealed system 120. Thus, e.g., evaporator 128 may be between and in fluid communication with second condenser 126 and compressor 122. During operation of sealed system 120, refrigerant may flow from evaporator 128 through compressor 122. For example, refrigerant may exit evaporator 128 as a fluid in the form of a superheated vapor and/or high quality vapor mixture. Upon exiting evaporator 128, the refrigerant may enter compressor 122. Compressor 122 may be operable to compress the refrigerant. Accordingly, the pressure and temperature of the refrigerant may be increased in compressor 122 such that the refrigerant becomes a superheated vapor.

Each condenser 124, 126 may be assembled in a heat exchange relationship with tank 112 in order to heat water within interior volume 114 of tank 112 during operation of sealed system 120. First condenser 124 may be positioned downstream of and in fluid communication with compressor 122, and may be operable to heat the water within interior volume 114 using energy from the refrigerant. For example, the superheated vapor from compressor 122 may enter first condenser 124 wherein it transfers energy to the water within tank 112 and condenses into a saturated liquid and/or liquid vapor mixture. Second condenser 126 may be positioned downstream of and in fluid communication with first condenser 124, and may additionally be operable to heat the water within interior volume 114 using energy from the refrigerant, such as by further condensing the refrigerant.

Sealed system 120 may also include a first throttling device 130 between first condenser 124 and second condenser 126, and/or a second throttling device 132 between second condenser 126 and evaporator 128. Refrigerant, which may be in the form saturated liquid vapor mixture, may exit first condenser 124 and travel through first throttling device 130 before flowing through second condenser 126. First throttling device 130 may generally expand the refrigerant, lowering the pressure and temperature thereof. The refrigerant may then be flowed through second condenser 126. Similarly, refrigerant, which may be in the form of high quality/saturated liquid vapor mixture, may exit second condenser 126 and travel through second throttling device 132 before flowing through evaporator 128. Second throttling device 132 may generally expand the refrigerant, lowering the pressure and temperature thereof. The refrigerant may then be flowed through evaporator 128.

First and second throttling devices 130, 132 may be any suitable components for generally expanding the refrigerant. For example, in some exemplary embodiments, first and second throttling device 130, 132 may be a Joule-Thomson expansion valve, also known as a “J-T valve.” In other exemplary embodiments, first and second throttling device 130, 132 may be an ejector. In still other exemplary embodiments, a capillary tube, fixed orifice, or other suitable apparatus may be utilized as first and second throttling device 130, 132.

Water heater appliance 100 may additionally include a temperature sensor 152. Temperature sensor 152 may be configured for measuring a temperature of water within interior volume 114 of tank 112. Temperature sensor 152 can be positioned at any suitable location within water heater appliance 100. For example, temperature sensor 152 may be positioned on tank 112 outside of interior volume 114 of tank 112, e.g., at upper portion 160 of tank 112. When mounted to tank 112 outside of interior volume 114 of tank 112, temperature sensor 152 can be configured for indirectly measuring the temperature of water within interior volume 114 of tank 112. For example, temperature sensor 152 can measure the temperature of tank 112 and correlate the temperature of tank 112 to the temperature of water within interior volume 114 of tank 112. Temperature sensor 152 may be any suitable temperature sensor. For example, temperature sensor 152 may be a thermocouple or a thermistor.

Water heater appliance 100 may further include a controller 150 that regulates operation of water heater appliance 100. Controller 150 may be, for example, in operative communication with sealed system 120 (such as compressor 122, and/or other components thereof), auxiliary heating elements, and/or temperature sensor 152. Thus, controller 150 can selectively activate system 120 and/or auxiliary heating elements 118, 119 in order to heat water within interior volume 114 of tank 112.

Controller 150 includes memory and one or more processing devices such as microprocessors, CPUs or the like, such as general or special purpose microprocessors operable to execute programming instructions or micro-control code associated with operation of water heater appliance 100. The memory can represent random access memory such as DRAM, or read only memory such as ROM or FLASH. The processor executes programming instructions stored in the memory. The memory can be a separate component from the processor or can be included onboard within the processor. Alternatively, controller 150 may be constructed without using a microprocessor, e.g., using a combination of discrete analog and/or digital logic circuitry (such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software.

As discussed above, water heater appliance 100 includes temperature sensor 152. Temperature sensor 152 may generally sense the temperature in the appliance 100, such as of water within interior volume 114 of tank 112, and may for example be in operative communication with controller 150. As discussed, temperature sensor 152 may measure temperature decay and facilitate flow detection when cold water is flowing through cold water conduit 104.

FIG. 3 provides a side partial, sectional view of certain components of water heater appliance 100, including tank 112, upper heating element 118 and temperature sensor 152. In exemplary embodiments as illustrated, temperature sensor 152 is configured on an outer surface 170 of tank 112. Temperature sensor 152 may for example be connected to the outer surface 170 using suitable mechanical fasteners, or may be mounted using, for example, an adhesive, welding, brazing, etc. A target sensor location 174 may be defined on an inner surface 172 of tank 112 at the location on tank 112 wherein temperature sensor 152 is located. In other words, target sensor location 174 may be the mirror location on inner surface 172 of the location of temperature sensor 152 on outer surface 170, relative to tank 112 wall.

In FIG. 3, cold water conduit 104 is positioned and oriented in order to assist accurate temperature decay and flow event detection for water heater appliance 100. In particular, as shown in FIG. 3, cold water conduit 104 includes an auxiliary aperture 180 defined therein. Auxiliary aperture 180 allows a portion of water flowing through cold water conduit 104 to flow therefrom. Auxiliary aperture 180 may also assist with hindering siphoning of water from tank 112 via cold water conduit 104. Auxiliary aperture 180 may be positioned at upper portion 160 of tank 112, e.g., about (e.g., within four inches of) a top wall of tank 112.

Auxiliary aperture 180 is aligned (e.g., positioned and oriented) such that temperature sensor 152 detects water exhausted through the auxiliary aperture 180. For example, such water exhausted from the auxiliary aperture 180 may contact a location on tank 112 relative to the temperature sensor 152, such as the target sensor location 174 or a location proximate the target sensor location 174. Thus, auxiliary aperture 180 may be aligned with the temperature sensor 152. In particular, auxiliary aperture 180 and temperature sensor 152 may be positioned at about (e.g., within about ten inches) a common height along the vertical direction V.

Referring to FIG. 3, desired alignment of auxiliary aperture 180 with temperature sensor 152 is illustrated, with reference arrow 182 indicating the direction of water flow. Such alignment is generally with respect to specific orientations about an axis defined by the vertical direction V, rather than relative to specific locations along the vertical direction. For example, in general, the auxiliary aperture 180 may be at any suitable location above the temperature sensor 152 along the vertical direction V. However, it is desirable that the auxiliary aperture 180 be aligned with the temperature sensor 152 about the vertical direction. Thus, water from auxiliary aperture 180 may directed towards temperature sensor 152 along a direction that is perpendicular to the vertical direction V.

FIG. 4 provides a perspective view of certain components of water heater appliance 100. As may be seen in FIG. 4, upper heating element 118, lower heating element 119 and temperature sensor 152 are mounted to tank 112. In particular, upper heating element 118, lower heating element 119 and temperature sensor 152 may be positioned on tank 112 such that upper heating element 118, lower heating element 119 and temperature sensor 152 are positioned collinear or plumb with one another on tank 112. Thus, upper heating element 118 may be positioned on the same side of tank 112 as temperature sensor 152.

As may be seen in FIG. 4, upper heating element 118 is positioned below temperature sensor 152 along the vertical direction V. Similarly, lower heating element 119 is positioned below upper heating element 118 (and temperature sensor 152) along the vertical direction. Thus, temperature sensor 152 is positioned above upper heating element 118 and lower heating element 119 along the vertical direction V on tank 112. As discussed above, upper heating element 118 may be positioned on the same side of tank 112 as temperature sensor 152. Thus, upper heating element 118 may be positioned directly below temperature sensor 152 along the vertical direction V on tank 112. Temperature sensor 152 may be positioned at or adjacent upper portion 160 of tank 112, and lower heating element 119 may be positioned at or adjacent lower portion 162 of tank 112. Upper heating element 118 is positioned between temperature sensor 152 and lower heating element 119, e.g., at a middle portion 103 of tank 112 between upper and lower portions 160, 162 of tank 112.

Upper heating element 118 may be positioned below temperature sensor 152 by any suitable distance. For example, upper heating element 118 may be spaced apart from temperature sensor 152 by a distance, d, along the vertical direction V. The distance can be any suitable distance. For example, the distance d may be greater than one inch and less than twenty-four inches. As another example, the distance d may be greater than five inches and less than twenty-four inches. As another example, the distance d may be about (e.g., within two inches of) eight inches.

Positioning upper heating element 118 below temperature sensor 152 may assist with intensifying heat applied by upper heating element 118 into a larger portion of interior volume 114 of tank 112. In addition, such positioning may allow water from auxiliary aperture 180 to be directed towards temperature sensor 152 in order to assist temperature sensor 152 with measuring the temperature of water from auxiliary aperture 180, e.g. in order to estimate flow rate, water use, and current hot water capacity. Thus, a first hour delivery rating of water heater appliance 100 may be improved while allowing temperature sensor 152 to control or regulate operation of sealed system 120, upper heating element 118 and lower heating element 119.

As may be seen in FIG. 4, first and second condensers 124, 126 of sealed system 120 are positioned on and wound about an outer surface 170 of tank 112. In particular, first and second condensers 124, 126 of sealed system 120 are positioned on an outer surface 170 of tank 112 at a bottom half of tank 112, e.g., such that first condenser 124 and second condenser 126 of sealed system 120 are positioned at or adjacent lower portion 162 of tank 112. As another example, first and second condensers 124, 126 of sealed system 120 may be wound about outer surface 170 of tank 112 such that windings of first and second condensers 124, 126 are positioned on a bottom third of tank 112.

Turning back to FIG. 3, cold water conduit 104 includes a dip tube 190. Dip tube 190 is mounted to tank 112 and extends into interior volume 114 of tank 112, e.g., downwardly along the vertical direction V. Thus, dip tube 190 may be mounted to tank 112 at upper portion 160 of tank 112. FIG. 5 provides an elevation view of a distal end portion 196 of dip tube 190. FIG. 6 provides a perspective view of distal end portion 196 of dip tube 190. As may be seen in FIGS. 5 and 6, dip tube 190 includes a tube wall 192 and an end cap 194. Tube wall 192 extends from tank 112 into interior volume 114 of tank 112, e.g., and defines auxiliary outlet 180. End cap 194 is mounted to tube wall 192 at distal end portion 196 of dip tube 190.

Tube wall 192 defines a plurality of outlets 198 adjacent distal end portion 196 of dip tube 190. Outlets 198 are positioned above end cap 194 along the vertical direction V. End cap 194 hinders or blocks water from exiting dip tube 190 at distal end portion 196 of dip tube 190. Conversely, outlets 198 permit water to flow out of dip tube 190. Outlets 198 may be positioned and oriented such that water flowing from outlets 198 is substantially horizontal or perpendicular to the vertical direction V. Thus, outlets 198 may hinder or limit mixing of water within interior volume 114 of tank 112 and encourage or assist thermal stratification of water within interior volume 114 of tank 112.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

What is claimed is:
 1. A water heater appliance defining a vertical direction, the water heater appliance comprising: a tank defining an interior volume; a sealed system configured for heating water within the interior volume of the tank; a dip tube mounted to the tank, the dip tube extending into the interior volume of the tank; a temperature sensor mounted an outer surface of the tank, the temperature sensor configured for measuring a temperature of water within the interior volume of the tank; and an electric heating element mounted to the tank, at least a portion of the electric heating element positioned within the interior volume of the tank, the electric heating element positioned below the temperature sensor along the vertical direction, the electric heating element spaced apart from the temperature sensor along the vertical direction by a distance, the distance being greater than one inch and less than twenty-four inches.
 2. The water heater appliance of claim 1, wherein the temperature sensor and the electric heating element are positioned on the tank such that the electric heating element is positioned directly below the temperature sensor along the vertical direction.
 3. The water heater appliance of claim 1, wherein the distance is about eight inches.
 4. The water heater appliance of claim 1, wherein the sealed system comprises a condenser positioned on the outer surface of the tank at a bottom half of the tank.
 5. The water heater appliance of claim 4, wherein the condenser is wound about the outer surface of the tank such that windings of the condenser are positioned on a bottom third of the tank.
 6. The water heater appliance of claim 1, wherein the dip tube defines an auxiliary aperture, the auxiliary aperture aligned with the temperature sensor such that water exiting the dip tube via the auxiliary aperture is directed towards the temperature sensor.
 7. The water heater appliance of claim 6, wherein the auxiliary aperture and the temperature sensor are positioned at a common height along the vertical direction.
 8. The water heater appliance of claim 1, wherein the electric heating element is a first electric heating element, the water heater appliance further comprising a second electric heating element positioned below the first electric heating element at a bottom portion of the tank.
 9. The water heater appliance of claim 1, wherein the temperature sensor is the only temperature sensor positioned on the tank that is configured for measuring the temperature of water within the interior volume of the tank.
 10. The water heater appliance of claim 1, wherein the dip tube comprises a tube wall and an end cap, the end cap mounted to the tube wall at a distal end portion of the tube wall, the tube wall defining a plurality of outlets adjacent the distal end portion of the tube wall, the plurality of outlets positioned above the end cap along the vertical direction.
 11. A heat pump water heater appliance defining a vertical direction, the heat pump water heater appliance comprising: a tank defining an interior volume, the tank extending between a top portion and a bottom portion along the vertical direction; a shroud positioned at the top portion of the tank; a sealed system configured for heating water within the interior volume of the tank, the sealed system comprising a compressor, an evaporator and a condenser, the compressor and evaporator positioned within the shroud, the condenser positioned on the tank; a dip tube mounted to the tank at the top portion of the tank, the dip tube extending downwardly along the vertical direction into the interior volume of the tank; a temperature sensor positioned at an outer surface of the tank, the temperature sensor configured for measuring a temperature of water within the interior volume of the tank; and an electric heating element mounted to the tank and extending into the interior volume of the tank, the electric heating element configured for heating water within the interior volume of the tank, the electric heating element positioned below the temperature sensor along the vertical direction by a distance, the distance being greater than one inch.
 12. The heat pump water heater appliance of claim 11, wherein the temperature sensor and the electric heating element are positioned on the tank such that the electric heating element is positioned directly below the temperature sensor along the vertical direction.
 13. The heat pump water heater appliance of claim 11, wherein the distance is about eight inches.
 14. The heat pump water heater appliance of claim 11, wherein the condenser is positioned on the outer surface of the tank at the bottom portion of the tank.
 15. The heat pump water heater appliance of claim 14, wherein the condenser is wound about the outer surface of the tank such that windings of the condenser are positioned on a bottom third of the tank.
 16. The heat pump water heater appliance of claim 11, wherein the dip tube defines an auxiliary aperture, the auxiliary aperture aligned with the temperature sensor such that water exiting the dip tube via the auxiliary aperture is directed towards the temperature sensor.
 17. The heat pump water heater appliance of claim 16, wherein the auxiliary aperture and the temperature sensor are positioned at a common height along the vertical direction.
 18. The heat pump water heater appliance of claim 11, wherein the electric heating element is a first electric heating element, the water heater appliance further comprising a second electric heating element positioned below the first electric heating element along the vertical direction, the second electric heating element positioned at the bottom portion of the tank.
 19. The heat pump water heater appliance of claim 11, wherein the temperature sensor is the only temperature sensor positioned on the tank that is configured for measuring the temperature of water within the interior volume of the tank.
 20. The heat pump water heater appliance of claim 11, wherein the dip tube comprises a tube wall and an end cap, the end cap mounted to the tube wall at a distal end portion of the tube wall, the tube wall defining a plurality of outlets adjacent the distal end portion of the tube wall, the plurality of outlets positioned above the end cap along the vertical direction. 